Due to the fact that all DRAM manufacturers focus more on the mobile sector at this point and also in the near future I don´t think we will see DDR4 prices decrease by any meanings. Unfortunately I think the prices will even increase more.
The prices are quite crazy I have to admit... I mean I payed for 32GB 3466MHz G.Skill more than for the freaking X299 motherboard...

Yeah I´m well aware of that but I was just stating that you will need the raw rendering horse power if you have a display with more Hz or higher resolution. But I would prefer a display (other than my 4K where 60Hz is obviously max right now) with more than 60Hz for gaming. I just hate tearing to death, just as much as micro stuttering from multi GPUs. So either FreeSync or G-Sync or 144Hz if it´s not 2160p.

You can run Freesync monitors with nVidia cards and G-Sync monitors with AMD cards, just without their individual technology. But the monitor will still run with the max Hz rate if your GPU is able to produce the amount of FPS. That being said if you´re looking into 144Hz 1440p it´s going to be much harder than 60Hz 1440p i.e.

If you want top TIER aka enthusiast cards you will probably have to wait until Q2 2017. I don´t think personally we will get to see anything but performance solutions this year. Many sites see things pretty much the same. The rumors (and it´s nothing but that right now for the most part) don´t indicate any enthusiast cards by this year.
HBM2 needs more time and I don´t think that GloFo or TSMC have the yield rates to go with big chips in 14/16nm yet. I personally run just 1 4K G-Sync monitor here and I´d be happy for something with a lot more raw rendering horse power in order to get rid of SLI (or for the matter CF) based issues, such as scaling, stuttering or missing profiles.
My guess is whatever AMD and nVidia will bring as next gen enthusiast card will be the first time ever a card to handle 4K as single card properly.

The build is rock solid for 1080p gaming and gives you even more headroom for upgrading in the future.
Well I went this route, because your budget is too tight for a system SSD and a storage SSD IMHO. Storage should be considered at elast 1 TB+ for games, data, music, etc.
This build allows you to put the OS on the SSD and your favorite games and all other stuff is just fine on a slower disk. I personally use HDD´s here for my rendering and compressing as cache drives.